Foren

Are there any specific estimates of the effect of A/C usage on range. The site says that there is an estimated range of 300 miles per charge for the S car. If you live in a hot climate like Arizona or Florida the A/C will be on most of the time. Does anyone know the cost in terms of range per charge if the A/C is constantly running. Does the range drop from 300 miles to 200? 100?

Todd Burch | 27. Juli 2010

I haven't done the math here, so someone who has can correct me...but it's going to affect your range on the order of a couple dozen miles at most. Certainly nowhere near 100 miles.

It's not a direct comparison at all, but you can gain perspective on the general relative values this way: How much does A/C affect range in a gas-powered car? Should have similar ballpark values.

In other words, for an internal combustion engine car that gets 300 miles to a tank with no A/C...you might get 275 miles per tank with the A/C running...something on that order.

An electric car is going to see approximately the same effects.

Douglas3 | 27. Juli 2010

From the ammeter, it looks like my Roadster consumes roughly 6A running the A/C when it is stationary; at 400V that's 2.4kW.

If you're driving a Roadster at 55 mph, the car requires about 12.5kW. So with A/C that will now 14.9kW.

53kWh battery capacity with 12.5kW consumption gives 4.24 hours of travel. Since we're going at 55 mph for 4.24 hours, the distance traveled is 233 miles. That matches the published performance curve.

53kWh battery capacity with 14.9kW consumption gives 3.56 hours of travel at 55 mph, for a distance of 195 miles.

That indicates the Roadster's A/C might reduce the range by about 16% or 38 miles.

ZenMasta | 29. Juli 2010

If your 16%/38mi is accurate that's only about 50 cents of electricity from your utility company?

Douglas3 | 29. Juli 2010

Sure, it's not much. Plus that was assuming A/C going full blast the whole trip.

Gregory_ | 1. August 2010

Caleb and Todd,

when I test drove the Roadster here in Hong Kong a couple of months ago, I asked the representative that exact question. his answer was:

(a) they won't have exact figures until the car has been manufactured, but...

(b) because there are no pulleys and belts wasting power, the A/C in Tesla's EVs use far less power than a traditional combustion engine would.

cheers,
Gregory

veer | 1. August 2010

Douglas,

You mention only 12.5kW needed to run at speeds of 55mph. And the sum total battery capacity needed is only 53kWH.

I figure your numbers are right because you are a Tesla Roadster owner as mentioned above.

A simple math for an IC car running 55mph at fuel consumption of 25mpg gives about 59kW.

This comparison is a huge selling point for Tesla. That is if the numbers of 12.5kW are right. The Roadster battery has to be near 98% efficient at generating power and its weight roughly 70% of the IC engine driven cars.

Once again thanks for the data. And Tesla must note the huge advantage as a selling point.

veer

ChadS | 1. August 2010

Douglas' numbers sound good. A/C does have a bigger percentage hit on EVs than gas cars just because EVs are more efficient, but then again Tesla uses a heat pump for A/C that is pretty efficient.

The only possible bugaboo with the 16% number is if you are in really slow traffic. The energy for propulsion is mostly based on how fast you are going, but the energy for HVAC is mostly based on how long you're using it. If you are in stop-and-go, the percentage hit of the HVAC could go way up. But then, because you are going slow, the amount of time it could last could go up too. You would have to be in the car for many hours for it to be a real problem.

Douglas3 | 2. August 2010

I don't think slow traffic will be an issue. The peak efficiency for the Roadster is under 20 mph. At that speed you can drive 400 miles, but it would take 20 hours! (In traffic you will also use regen braking a lot, so stop and go isn't that big a deal.)

If you did nothing but run the A/C the battery would last about 22 hours.

So with the A/C going continuously full blast you can "only" drive for 10 hours at 20 mph. Still going 200 miles.

Of course the numbers won't be exactly the same for the Model S, but we're in the ballpark.

Doug

Naburus | 5. August 2010

I have seen this mentioned in another area of this forum, but, couldn't you increase the range of a single charge on these batteries if you installed a small scoop, either on the side of the car, or underneath the car, with a wind turbine inside, which uses a flapped propeller to catch the jet stream as you drive and regenerate electricity in the batteries. I can't imagine the cost of this design change being particularly high, so it shouldn't cost too much to the consumer to make the addition. I haven't considered any mathematics of the add, but, I would think if the alternator in a car can recharge a battery practically indefinitely, a couple small generators in a tesla could get your at least another 100 miles out of each full charge. Depending on the speed you've been driving of course.

What do you all think?

Douglas3 | 5. August 2010

Naburus, that's a perpetual motion machine. A physical impossibility. Doing that will decrease mileage due to losses in the system, not increase it.

Brian H | 20. August 2010

Douglas3;
yeah, there seems to be an unending supply of these guys who are prepared to spend 10¢ to make 5¢. A fool and his money ... ;)

searcher | 4. September 2011

What is wrong with the "general forum" can't locate my thread that was active 09/02/11. Bunch of garbage on there and latest post 2010? I was discussing unemployent in various countries. If anybody thinks this is irrelevant to Tesla sales I will be glad to show them otherwise. Surely some geek doesn't think potential Tesla buyers are impervious to the effects of unemployment just because they may belong to professional class. If they do I can easily show them where they are wrong as many of the professional class income come directly and solely from the tax base. So again where is my "freaking thread" esoteric EV ramblings or as the case may be "freaky thread". LOL.

searcher | 4. September 2011

Timo told me how to find it. Thanks and pardon the off subject interuption.

Ramon123 | 4. November 2011

Don't compare the electrical penalty for the roadster with a sedan like the Model S, which has probably three times the interior volume to cool and more glass. The amount of cooling required will be
based on 1) the outside temperature and solar gain thru the windows, the amount of thermal insulation, the number of passengers, the state of the car at the beginning of the trip, the amount of time the AC is run and the desired interior temps. Speed will affect the amount of
hot air brushing the exterior surfaces. It would be wise to pre condition the vehicle while it is still plugged in before starting out. The AC unit will not have a continuous draw - it will cycle
the compressor/fan on and off just like any other heat pump. There
is no answer to the question "How much penalty from AC usage."
The question has to be much more specific before any answer can be calculated. One would need, at a minimum, a wattmeter to measure
the battery pack output over time, but preferably would want a wattmeter hooked up to the heat pump. With that in place, one could
carry out experiments and start to nail down the answer for several
conditions. As for the claim that "pulleys and belts" makes a Tesla heat pump superior to what's found in an ICE vehicle, that is pure nonsense. First, those belts and pulleys" don't impose any significant energy penalty. Second, when talking about heating a
car, a gasoline engine makes plenty of heat as a free by product of
burning fuel - heating a gas powered car doesn't require any appreciable energy, other than a distribution fan (and often not even that), whereas the Tesla heat pump in heat mode will extract a very large penalty I suspect. In the same way that is costs a whole lot more to heat a house than to cool a house using a heat pump.
So when it comes to HVAC, look for heating to be the big energy drain on the battery. That's my guesstimate.

sarge7359 | 4. November 2011

Though the original question wasn't about heating, I suspect ICE energy loss vs EV would prolly be about even. Those pulleys and pumps in the ICE don't run for free, nevermind the electrical for pushing air through the heat exchanger since running the alternator already (a constant small drain). Meanwhile the EV just has to run a heat pump and fans for a relatively small area versus a house.

A gas furnace may be cheaper to heat a house vs the heat pump, but I'm not putting one of those in my car. ;-)

Regarding AC measurement above, it was worst case: running AC full blast and see the difference. I agree that actual cooling load would be much less.

brianman | 5. November 2011

"oline engine makes plenty of heat as a free by product of
burning fuel - heating a gas powered car doesn't require any appreciable energy, other than a distribution fan"

From a Tesla rep at the Bellevue opening...

A similar situation applies for the S. Cooling of the battery and heating of the cabin interact in a similar way. At least that's what was asserted.

Brian H | 6. November 2011

As for interior space to cool/heat, the surface area of a small car is a higher ratio to the interior, so heat loss/gain is more significant. So there's some trade-off for the S.